The flywheel has long been used to store energy. It is a relatively simple device from which it is possible to store and retrieve energy readily, either by mechanical means or by using electric motors and generators. Attempts have been made to maximize the rotational inertia of the flywheel, thereby increasing the flywheel's energy storage capability by placing as much mass as possible at the outer portion of the radius or rotor. The more mass or weight of rim material required by the intended use of the flywheel, the more rigidity or strength is required to meet the loads without self-destruction of the flywheel. The present invention provides an inertia flywheel comprising a rotor contained within a partial wrap harness of suitable material terminating in a series of adjustable strap tensioners attached to a hub with a suitable tensioning nut or similar device. A wheel and axle are typically connected with spokes and/or a rim. Unlike the spokes of a wagon wheel that hold the rim away from the hub, the present invention operates similar to a bicycle or motorcycle wheel where the spokes are tensioned and torqued to pull the rim of the wheel toward the hub. The present invention creates additional strength by tensioning (pulling) the rotor toward the hub, allowing for the use of much heavier materials in the rotor and much lighter materials in the wrap harness, strap tensioners and hub. In a preferred embodiment, the rotor is liquid filled and includes suitable one-way valves such as the Variable Inertia Flywheel of U.S. patent application Ser. No. 11/833,611.